1. Field of the Invention
This invention relates to the manufacture of integrated circuit devices. In particular, it relates to a system for connecting metallic leads to a semiconductor chip.
2. Prior Art
In the manufacture of semiconductor devices, the connection of metallic leads to individual chips remain a significant manufacturing problem. Typically, a large number of metallic interconnections must be coupled to an individual chip about its perimeter. One technique known in the technology is tape automatic bonding (T.A.B.) which utilizes a roll-type film cut to form an individual set of chip I/O leads. This individual set is formed by utilizing etch techniques to obtain a personalized lead pattern which conforms to a given chip terminal pattern (footprint). The etch pattern is used to create a large number of identical sets. An individual set is then introduced at the bonding station for affixation. The individual terminal ends of the leads are then coupled using thermal compression or AuSn bonding to the chip. All leads are connected to the chip simultaneously and by utilizing a continuous reel transport process system throughput is enhanced. Thus, T.A.B. is used to facilitate very high production rates for coupling a number of identical chip I/O's to outer circuitry.
A second known technique is wire bonding which, in contrast to T.A.B., is labor intensive. Wire bonding is advantageous since it affords flexibility in the placement of individual wires. The bonding tools can be used irrespective of the chip footprint. This is in contrast to the inflexibility of T.A.B. where a given footprint etched in the tape is tailored for a specific footprint of a chip. Thus, the tooling for bonding a particular chip is dedicated for that chip size and lead pattern. It has no other utilization. Wire bonding techniques while slower in overall production speed can be tailored to accommodate disparities in chip configuration. Given these two known techniques, T.A.B. is generally applied to very high production runs relative to wire bonding.
A second disadvantage of T.A.B. is the long lead time necessary to obtain photoprocessed and etched full tape, personalized to a specific chip configuration. Additionally, quality control problems exist in T.A.B. systems. Such problems occur given variations in film thickness, etching, and actual bonding on a lead-by-lead basis. Additional problems arise in the storage, handling and transportation of pre-personallized foil tape.
Within the prior art, various subsystem components describe individual facets of these two techniques. For example, U.S. Pat. No. 3,698,075 and U.S. Pat. No. 3,709,424 disclose techniques of ultrasonic bonding of a sheet of personalized sheet structures to contact pads on a chip. Specifically, U.S. Pat. No. 3,698,075 provides a sheet metal strip having a large number of identical lead frame sections which are broken away as the sheet is unwound. The strip has a number of leads configured to match bonding pads on a chip. The strip is placed on a mounting pedestal and the chip then placed face down so that the bonding pads contact the leads. Bonding takes place utilizing a needle which is ultrasonically stimulated.
U.S. Pat. No. 3,709,424 also employs a continuous sheet having a plurality of lead structure sections which are placed over a chip mounted on a pedestal. The pattern is personalized for the lead structure of the particular chip. Bonding occurs either by the application of heat or utilizing an ultrasonic transducer contacting each bonding point.
Computer control for the placement of lead wires is disclosed in U.S. Pat. No. 3,737,983. Specifically, the system utilizes a series of chucks which are indexed to various work stations. The work stations contain wire loading devices, an alloy station for placing semiconductor devices in a predetermined orientation on the head of one of the wire leads and a series of automatic bonding stations for connecting the base and emitter contacts of the semiconductor devices to the head of the other wire leads. The system operates under computer control having a general purpose digital computer which is programmed to monitor operation at various stations and locate any chuck which is defective so that the production process does not continue for defectively fabricated device.
Other prior art relating to the production of semiconductor devices, and in particular, lead structures and their bonding to integrated circuit chips are found in U.S. Pat. Nos. 3,395,447; 3,544,857; 3,698,074; 3,793,714; 3,846,905; 3,859,715; 3,859,718; and 4,079,509. While this prior art defines various steps, in none is there any integrated process for fabricating personalized leads used for tape bonding and, bonding those leads to a particular chip. The ability to vary either the pattern cut from the metal tape on a real time basis for a particular chip or to personalize the bonding for the unique geometry of that chip is not found within the prior art germane to the manufacture of integrated circuit structures.
Computer controlled cutting systems, for example, in the manufacture of garments, are known where the cutting operation is in response to a stored program. For example, U.S. Pat. No. 3,761,675 and 4,178,820 are directed to computer controlled techniques for cutting pattern pieces from computer generated markers. The '675 patent utilizes a laser cutting system wherein the cutting tool is under computer control having stored therein a program indicative of the particular marker. The pattern data is fed to the computer which then organizes the pieces within a sheet to minimize selvage. This orientation of the pieces, the marker, is then stored and the outlines are utilized to control the cutter's trace. Similarly, the '820 patent utilizes a blade cutter operating under computer control to delineate the cutting path relative to the cutting table.
A hallmark characteristic of both of these systems is that the patterns which are cut define components of an overall apparel pattern. Those individual components following cutting are separated from the selvage and are then individually assembled into the completed garment. Thus, while computer control is utilized for initial cutting of components, all fabrication steps following the actual cutting process are accomplished by hand. Other computerized cutting systems are found in U.S. Pat. Nos. 3,490,320 and 3,761,675. Also, the particular marker is dedicated to one garment.
Thus, within the prior art, broadly pertinent to the concepts of cutting a required pattern from a strip of material within the art related to pattern cutting, once the components have in fact been produced from the strip they must then be assembled by hand. Within the technology specifically germane to the fabrication of semiconductor elements, there is no such personalization at either the cutting step or the bonding step. Rather, a repetitious pattern is created in T.A.B. techniques and repetitious bonding utilizing dedicated tools occurs at a subsequent station. Thus, to the extent that computer control techniques are utilized, they are inflexible and dedicated to a given footprint of the bonding conductors dedicated to a specific chip footprint.